Historically, cooling a data center was a straight-forward matter. Data centers used to generate less power and, consequently, less heat per square foot than modern counterparts. As a result, a technician could simply offset the heat from the equipment by adding additional computer room air conditioning (CRAC) units inside the data center, and there was little need to develop or implement a complex system for monitoring and controlling data room cooling. However, the increase in computer room power consumption, density, and heat generation now requires a more scientific approach to monitoring and controlling computer room data center than ever before.
Because of the density of equipment in most data rooms, technicians have implemented a variety of techniques to improve cooling. For example, in many instances, data equipment is placed on raised floors, two tiles apart, with their air intakes facing each other to achieve the air circulation necessary to keep the computer room cool. In this configuration, CRAC units pump cool air through perforated floor tiles between the racks, the computers and racks intake the cool air and exhaust hot air into the opposing, hot aisle. Computer room air conditioning units on the floor then pull in the hot air exhausted into the hot aisles, and release it underneath the floor tiles, completing the cycle. In this way, a series of CRAC units can keep cool air running through the system and help keep a steady airflow through the environment.
Alternatively, technicians may turn the area above racks into a hot air plenum by placing ducts and more CRAC units in this space. In this case, hot air escapes into the plenum to be pushed back into the system, below the floor, where it can be cooled and released back into the computer room. There are also a variety of other techniques and technologies for cooling data centers. However, in each case careful monitoring and control are required to be effective, and current methods of monitoring and control are obsolete, inefficient and ineffective for several reasons.
First, most current methods of cooling capacity measurement consist of the use of a balometer capture hood with pitot and temperature, humidity, and pressure sensors. Multiple readings are taken with the single device at multiple locations within the sampling area. The readings are then used to manually calculate the cooling measurements. This method is labor intensive, evasive, time consuming, and often inaccurate since, for example, the person taking the measurements may block or divert airflow and affect the results. Also, because of the time involved to take multiple measurements and calculate the results, meaningful information is not available in real time. CRAC manufactures may also attempt to calculate cooling parameters using temperature, humidity, and fan speed. However, this method also suffers from the inability to provide real time data.
Second, current methods of determining effective CRAC unit utilization can be very imprecise. The common methodology is to compare temperature change through the CRAC unit and compare it to the amount of compressor or chill water valve and fan speed. This method does not take into account all of the components required to measure heat capacity—temperature, pressure, water content, and quantity of airflow—and, therefore, cannot fully provide meaningful information about cooling capacity.
In addition, there is currently no efficient method of measuring mass air flow cooling distribution at vents or perforated raised floor tiles used in data rooms. The closest methodology only measures velocity and/or volume of air by using a pinwheel or hot wire anemometer, or a flow hood balometer. The anemometer displays only velocity of air (feet per minute) requiring several sample readings to be taken, and then airflow must be calculated (cubic feet per minute) using the average readings to the sampling area. The flow hood balometer uses a pitot array to measure pressure differentiation and temperature in a specified sampling area to provide a volume of airflow. As will be appreciated by those skilled in the art, neither of these methods account for the four components of mass air flow and are, therefore, ineffective means of measurement. The metrics used (velocity and airflow volume) are not consistent with the requirements for measuring cooling capacity metric (tons or watts) or heat load.
The only way to measure heat load and cooling consumption is to monitor the metered power consumption. Typical data center computers are mounted in a rack or cabinet. Generally, the rack orientates the equipment in a front to rear position. Data center operational best practices promotes the inflow of cooling into the front of the equipment/racks and the exhaust air out of the rear. As a result, mass air flow detection of heat load does not exist in the data center operation methodology. Consequently, there is no effective method for measuring the mass air flow and enthalpy change of data center load.
There is a need, therefore, for a method and system that provides an effective measurement and metric for cooling infrastructure and, more specifically, that can compare actual cooling capacity production to cooling infrastructure power consumption. Such a comparison will present an efficiency metric watts of cooling per watts of power consumption (watts per watts).